Papers by Keyword: Local Structure

Abstract: Cu-doped ZnO (CZO) with Cu %mole of 0, 13, 14, and 15% have been synthesized by the co-precipitation method with controlled pH at 9. The diffraction pattern of CZO shows that a single phase of ZnO with wurtzite structure (w-ZnO) was achieved in the parent compound. In contrast, small fractions of the secondary phase of CuO monoclinic (m-CuO) were identified in the doped compounds. Rietveld-refinement on the X-Ray Diffraction (XRD) patterns reveals that the crystallite size of CZO is estimated in the range of 84 - 148 nm with instrumental correction factor and that CZO14 exhibits the most considerable fraction of m-CuO among the samples. Interestingly, lattice constants decrease by Cu doping. The effects of Cu doping on the valence state and the local structure were investigated by X-Ray Absorption Spectroscopy (XAS). Based on our analysis on both Cu K-edge and Zn K-edge XANES spectra, oxidation states of Cu and Zn ions are about +2 with no evidence of other valence states. Cu atom is likely to incorporate into wurtzite crystal lattice by occupying Zn sites in a small portion, and the doped compounds create a few oxygen vacancies.

Abstract: The Nanpu 5th construct is in the western part of Huanghua Depression Nanpu Sag of Bohai Bay Basin, was a complicated anticline belt that develops between Jian Dong fault and the downthrown side of the southwestern Zhuang fault and the favorable exploration area is 120km2. On the basis of the region's large number of multi-channel seismic data analysis and interpretation, the trap types, structural characteristics and distribution of local structures between the layers of the region are researched. Interlayer local structures in the area are mainly divided into nose structure and small anticline. The fault zone is a structural high in the region, to promote oil and gas to migrate and accumulate to the low-potential zones that become favorable zones for hydrocarbon accumulation, but the real decisive construct parts of the hydrocarbon accumulation is positive local structure in favorable zones which point out the region for hydrocarbon accumulation.

Abstract: The microscopic structure and diffusion of liquid Cu₄₅Zr₄₈Al₇ alloys were investigated by means of molecular dynamics simulations. We obtain the structure and diffusion properties including partial pair-correlation function, and Voronoi indices and the time-dependent mean-square displacement (MSD). We found that the icosahedra and the distorted icosahedra around Cu, Zr and Al are differentthe and the atom moves quickly Zr, Cu and Al in the order.

Abstract: In this article, we show principles and advantages of anomalous x-ray scattering in combination with neutron scattering and reverse Monte Carlo modeling to characterize structures of non-crystalline materials, in particular, metallic glasses. Then, we briefly introduce examples of our recent applications to Pd₄₀Ni₄₀P₂₀ and Zr₆₃Ni₂₅Al₁₂ bulk metallic glasses having good glass-forming abilities.

Abstract: The problem of face classification is essentially a nonlinear subspace classification problem. The features of different face samples lie on different nonlinear subspaces. If the most representative samples of each subspace are selected as the training set, we can enhance the reliability of the classification, as well as reduce the computation. In this paper, a manifold based active learning algorithm, called Laplacian Transductive Optimal Design (LTOD), is presented to select the most representative samples. LTOD reconstructs each sample by the graph Laplacian matrix to make sure that the reconstructed samples and the original samples share the same manifold structure. Then, the samples which can be used to best reconstruct the whole sample set are selected as the training set. The experimental results on Yale face database have demonstrated the effectiveness of our method.

Abstract: Phase characterization is critical in material properties probing. In this study, Raman scattering was employed to identify the phase of YSZ co-doped with CeO₂/Gd₂O₃. As a comparing, XRD for co-doped YSZ was also measured. The results show that introducing a small amount of CeO₂/Gd₂O₃ into YSZ can lead to a change on Raman spectroscopy. Raman peaks appear with co-doping is attributed to the local structure change which caused by the re-distribution of vacancy. Comparing to XRD, Raman spectroscopy shows a more sensitive on the phase identify for the YSZ with a small amount dopant.

Abstract: The La_1-xSr_xCoO₃ (x =0.0, 0.1, 0.2 and 0.3) samples were prepared by solid-state reaction method. The X-ray diffraction patterns show that the samples are of R-3c spacegroup and the relative intensity of (024) plane diffraction peak increases with the increase of Sr concentration. The x-ray absorption fine structure data of Co ions can be fitted with 2 and 3 different scattering paths for the samples with x=0, 0.1 and for x=0.2 and 0.3, respectively. A new peak arises in x-ray absorption spectra of O ions. These results suggest a relationship between the variations of electron densities and local structure distortion. Both the valence band photoemission and x-ray absorption spectra indicate the existence of possible phase separation scenario that comes from the different types of Co-O bonds which coexist in one sample.

Abstract: The microscopic structure Cu₄₆Zr₄₆Al₈ alloys were investigated by means of molecular dynamics simulations. This work gives the structure properties including partial pair-correlation function, pair analysis technique and Voronoi indices, and the temperature dependence. The simulated pair-correlation function is consistent well with the experimental one. We found that the the fractions of icosahedra and the distorted icosahedra increase with the decreasing temperature and become into the dominant clusters in the bulk metallic glass. At the meanwhile, we found that the icosahedra and the distorted icosahedra around Cu, Zr and Al are different. The Cu-center and Al-center icosahedra and the distorted icosahedra increase with the decreasing temperature, but The Zr-center icosahedra and the distorted icosahedra decrease with the decreasing temperature.

Abstract: The local structure evolution of polyacrylonitrile (PAN) fibers during pre-oxidation and carbonization was studied using X-ray diffraction (XRD) and radial distribution function (RDF). The nearest inter-chains distance of PAN is 6.88 Å, which is close to the diameter of the “rigid rod” model proposed by Warner. The third neighbor distances of carbon fibers are greater than that of graphite, indicating the planar six-member rings are absent in the carbon fibers from 500 to 1250°C. The structure of fibers transforms from long-range order to long-range disorder during the pre-oxidation process, then transforms from short-range order to long-range order during the carbonization process.

Abstract: Using ANSYS to carry out finite element analysis of joint of end floor beam and main longitudinal girder in certain compound platform, researching on stress distribution of the joint, and making detailed analysis according to the calculation result of node finite element, the paper finds out the reason for crack of the joint and presents the improved design which enhance the carrying ability of the structure. The calculation result can also provide reference for other similar problems with different section form.